muffler and cat glowing red

my two chamber flowmaster and my cat get extremely hot glowing red, spitting flames one time. cat is almost brand new along with muffler and i can see through the screen so its not clogged. tranny fluid level is normal , but the exhaust exits out the back of the flowmaster so could it be i need to finish the exhaust to exit out the back? my engine is running rough am i possibly not firing on one piston and getting unburnt gas down in there ? 88 xj 4.0 does it at highway speeds up hill and crawling. thanks in advance for any ideas

must be running too rich...time to start checking all the simple stuff...could be a bad O2 helping it run rich...plenty of stuff to check though...dont melt the catalyst in your cat by running it that hot...can also melt your carpet inside...at a lot of auctions people swap the 5 and 7 spark plug wires to make it run rough...can heat the cat up a lot not burning the gas in the cylinders like its supposed to.

Something could be blocking the flow also. Be carefull where you park. Could start a grass fire

the way you're describing it running, sounds like its running rich.

rich fuel mix = high EGT

theres no carpet its just making the glue/paint smoke on the floor, and its wet right now every where i am so no worry about fires. i think its running rich , somone mentioned that to me prior to coming here. spark plugs are on right, the rest of the exhaust up to header is clear i took that off during my tranny swap and made sure.thanks for all the suggestions ill start checking

yellowxj said:

must be running too rich...time to start checking all the simple stuff...could be a bad O2 helping it run rich...plenty of stuff to check though...dont melt the catalyst in your cat by running it that hot...can also melt your carpet inside...at a lot of auctions people swap the 5 and 7 spark plug wires to make it run rough...can heat the cat up a lot not burning the gas in the cylinders like its supposed to.

Click to expand...

Yeah, that 7-cylinder never seems to run quite right on the 4.0l engines.

Red Hot Cat could be the result of a number of malfunctions including faulty oxygen sensor, an incorrect fuel mixture, worn spark plugs or plug wires, a faulty check valve, incorrect ignition timing, faulty fuel injectors, a failed fuel pressure regulator or other ignition malfunctions.